In concurrence with diversification of the sexual manners and customs and change in pattern of sexual behavior of the Japanese centering on the young people, an increase in the chlamydial infection as a sexually transmitted disease is significant today.
Chlamydia is an obligate intracellular parasitic bacterium of eukaryotic cell. Chlamydia grows and proliferates in a host cell, and forms an inclusion in the cytoplasm of the cell, and this causes clinical symptoms to the host. For example, the causative microorganism of genital chlamydial infection is Chlamydia trachomatis, which mainly develops the symptoms of urethritis in a man and cervicitis in a woman.
As a detection method of chlamydia, methods for detecting antigen, such as direct fluorescent antibody staining (DFA), enzyme immunoassay (EIA), and enzyme linked immunosorbent assay (ELISA), have been developed. In addition, a detection method for detecting Chlamydia trachomatis by probe hybridization technique using labeling substance-labeled single-stranded DNA which is complementary to the ribosomal RNA of Chlamydia trachomatis has also been developed (Gen-Probe Pace 2 Chlamydia test, Non-patent Literature 1).
Furthermore, a higher sensitive detection method utilized nucleic acid amplification technique has also been developed.
For example, Domeika et al. (Non-patent Literature 2), Bauwens et al. (Non-patent Literature 3), and specification of U.S. Pat. No. 5,232,829 (Patent Literature 1) have reported a method for detecting Chlamydia trachomatis by performing polymerase chain reaction (PCR) and subsequent microtitration plate hybridization.
In addition, a method for detecting Chlamydia trachomatis by performing ligase chain reaction (LCR) and subsequent microparticle sandwich immunoassay detection has also been reported (Non-patent Literature 4, Non-patent Literature 5 and Non-patent Literature 6).
Further, it has been known that Chlamydia trachomatis has multiple copies of endogenous plasmid specific for this bacterium (Non-patent Literature 7). And, a method for detecting Chlamydia trachomatis by using a particular sequence of this endogenous plasmid as a target, amplifying a part of the sequence thereof by a gene amplification method, and detecting the amplification products has been developed (Patent Literature 2, Patent Literature 3).
By the way, it has been known that there are 18 kinds of serologic type which were identified immunologically for Chlamydia trachomatis. And, in recent years, a case where Chlamydia trachomatis could not be detected by the above-described conventional detection method of Chlamydia trachomatis has been reported (Non-patent Literature 8). That is, it turned out that by the conventional detection method of Chlamydia trachomatis, there may be a case of providing a false negative detection, and it has been a problem.